Hi TravisNF,
When you select Combo Boxes in Developer tab and move the cursor to the sheet area, the mouse cursor changes to four arrows, at this time you can simply click the sheet to insert the Combo box. I tested on my
end and it does work in Excel 16.18 on Mojave 10.14.1.
If the issue persists, please provide the following information:
1.
When was the last time you inserted the combo box successfully in a new sheet?
2.
Did you make any changes recently in your computer?
3.
Please check if you have any custom add-ins installed. For this, click the Insert tab,
and then click My Add-ins. If you see any add-ins, please remove them and then check.
Thanks,
Neha